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Home -> Community -> Usenet -> c.d.o.server -> Re: Rollback performance and delete
> Oracle copies before image copies of all changed blocks into the
> rollback segment. So if your 1G of deleted data spread over 5G of
> data blocks, 5G will be written into rollback segment.
So far the above explanation is the only one I have seen to explain this. The index I have is about 1 G also, so if I delete 1G of data and 1/5th of the index, how does this result in a rollback segment that is >5G in size!
"Howard J. Rogers" wrote:
> "Alex Filonov" <afilonov_at_pro-ns.net> wrote in message
> news:8u7chm$3mn$1_at_nnrp1.deja.com...
> > In article <3A06DE5D.30933844_at_motorola.com>,
> > Allen <allen.brost_at_motorola.com> wrote:
> > > I have looked through the Oracle documenation to understand exactly
what the
> > > rollback segment is doing during a DELETE and I am still a little
confused with
> > > the results I am finding.
> > >
> > > I am doing a delete of a large table. The table is 5G. I am deleting
about 1G
> > > of the the table.
> > >
> > > I have created a large rollback segment to handle the transaction and
I have set
> > > the size of the rollback segment to about 2G. I figured that this
should be
> > > plenty. When I do the delete, I see the rollback segment grow to 5G.
I don't
> > > understand this. I thought the rollback segment held all of the
original rows
> > > before the change. If this is so, then I would expect to see about 1G
in the
> > > segment. It seems like Oracle is copying everything in the table to
the
> > > rollback segment. Anyone know why?
> > >
> > > - Allen
> >
> > Oracle copies before image copies of all changed blocks into the
> > rollback segment. So if your 1G of deleted data spread over 5G of
> > data blocks, 5G will be written into rollback segment.
>
>
>> > Sent via Deja.com http://www.deja.com/
> > >
> > >
> >
> >
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